1. Field of the Invention
The present invention relates to an ultrasonic imaging apparatus comprising a transmitting circuit and a receiving circuit of ultrasonic signals in an ultrasound probe. More specifically, the present invention relates to an ultrasonic imaging apparatus comprising test circuits of the transmitting circuit and the receiving circuit of ultrasonic signals.
2. Description of the Related Art
Conventionally, for an ultrasonic imaging apparatus that generates an ultrasonic tomographic image by sending out an ultrasound beam to a subject to be examined and receiving the reflected ultrasonic echo, a 1-dimension array probe on which reed-shaped piezoelectric elements are arranged in an array form is used.
Electronic scanning using a 1-dimension array probe allows electronic focusing and scanning of ultrasound beams within a surface in the direction of the arrangement of the piezoelectric elements. However, in the direction perpendicular to the direction of arrangement (i.e., the normal line direction of the ultrasonic scanning surface described above), it allows only focusing by using only an acoustic lens, so changes of the focal point are limited to within a narrow range. Therefore, it is difficult to focus various points on a two-dimensional plane. In addition, it is possible only to two-dimensionally scan an ultrasound beam because the arrangement of array elements is a one-dimensional arrangement.
Therefore, in order to realize omni-directional focusing and high-speed three-dimensional scanning, and to facilitate understanding of the structures within living bodies, a 2-dimension array probe in which ultrasonic transducers are arranged two-dimensionally and that allows delay-controlling in each of the two directions in which ultrasonic transducers are arranged has been proposed in recent years. (For example, see Japanese Unexamined Patent Application Publication 2005-319199.)
Subsequently, three-dimensional scanning has been conducted and stereoscopic images have been displayed by employing the 2-dimension array probe as described.
In addition, for 2-dimension array probes such as those with a 32×32 configuration, the number of transducers required is 1,024. In the 2-dimension array probe having the number of transducers as described, it is necessary to transmit/receive ultrasonic waves by using all transducers. In this case, 1,024 transducers are housed in a probe head to be placed in contact with a subject to be examined, so if they are connected to an ultrasonic imaging apparatus without change, 1,000 or more cables will be needed. The structure of such an ultrasound probe is impractical.
Furthermore, for the 2-dimension array probe, transducer impedance will increase because the shape of transducers is smaller than that of a conventional 1-dimension array probe. As a result, degradation of received echo becomes greater for the 2-dimension array probe. This lowers the amount of information used for forming images and makes proper diagnosis difficult.
Therefore, in order to efficiently supply a pulse for transmission and to minimize the degradation of received echoes, an ultrasonic imaging apparatus including a probe head with a configuration as shown in FIG. 1 has conventionally been proposed for the 2-dimension array probe. FIG. 1 is a diagram of a configuration of an ultrasonic imaging apparatus including a conventional 2-dimension array probe. This ultrasonic imaging apparatus, as shown in FIG. 1, incorporates in the probe head 110, a group of pulsers 112 for supplying a transmitted pulse to the proximity of a transducer 111 in a probe head 110, a transmission controller 113 for controlling the group of pulsers 112, a group of receiving electronic circuits 114 for amplifying the received echo, a receiving control circuit 115 for controlling the group of receiving electronic circuits 114, and a high-pressure prevention circuit 116 for protecting the group of receiving electronic circuits 114 from a high-voltage pulse outputted from the group of pulsers 112. Herein, the group of pulsers 112 is an aggregation of a plurality of pulsers, and hereinafter, when explaining one pulser, it is simply referred to as a pulser 112. In addition, hereinafter, an aggregation of a plurality of transducers 111 is referred to as a group of transducers 111.
Upon receiving a control signal such as a pulse production command from a body control circuit 015 that is housed in an ultrasonic imaging apparatus body 010, a probe control circuit 122 conducts a relocation of the data necessary to transmit a control signal or the like. Then, the probe control circuit 122 transmits the control signal to the transmission controller 113. Upon receiving the control signal, the transmission controller 113 transmits a timing signal for a pulse signal to the group of pulsers 112. Upon receiving the timing signal from the transmission controller 113, the group of pulsers 112 generates a pulse signal. The produced pulse signal causes the group of transducers 111 to oscillate and to send out an ultrasound beam to a subject to be examined 030, and then is received as the received echo that is a reflected wave through the group of transducers 111. A received echo signal that is based on the received echo received through the group of transducers 111 is sent to the group of receiving electronic circuits 114. The group of receiving electronic circuits 114 groups a plurality of channels as channels corresponding to the group of transducers 111 and performs local beamforming. This makes it possible to reduce the number of cables for the probe. For example, in the case of the 2-dimension array probe with the 32×32 configuration, assuming that there are 8 channels per group, the group of receiving electronic circuits 114 has 1,024 channels that correspond to the group of pulsers 112, which are reduced to 1,024/8 groups.
The received echo signal to which the local beamforming has been performed, is processed such as buffering in the group of signal-processing circuits 121 housed in a probe connecter 120, and then is entered into the ultrasonic imaging apparatus body 010. Herein, the probe control circuit 122 conducts setting of the group of signal-processing circuits 121 upon receiving a signal from the body control circuit 015. A beamforming is performed for the entire received echo signal in a group of receiving electronic circuits of the body 011. From the received echoes, all of which the received beamforming has been performed upon in the group of receiving electronic circuits of the body 011, an envelope signal corresponding to information in a living body or the like is extracted by a signal-processing circuit of the body 012. Furthermore, the received echo is converted to a desired display coordinate in an image-processing circuit 013 and is displayed on the displaying part 014.
In addition, the body control circuit 015 that is installed in the ultrasonic imaging apparatus body 010 controls each part of the ultrasonic imaging apparatus body 010 in accordance with parameter information entered from an inputting part 020, such as operation mode, scan mode, or display mode.
FIG. 2 is a diagram that represents the skeletal framework of a transmitting/receiving circuit with one channel when employing a pulser that transmits a unipolar pulse. FIG. 3 is a diagram that represents the skeletal framework of a transmitting/receiving circuit with one channel when employing a pulser that transmits a bipolar pulse.
Next, operations in the case of the unipolar pulser will be explained. As shown in FIG. 2, the pulser 112 has a level shifter 141, a pulse production FET 142, and a shunt field-effect transistor (FET) 143.
The transmission controller 113 transmits a timing signal to the pulser 112. The transmission controller 113 has a circuit that produces a timing signal for instructing the transducer 111 to generate an ultrasonic pulse and a timing signal for receiving a signal based on the ultrasonic echo from the transducer 111. Then, to instruct the transducer 111 to generate an ultrasonic pulse, the transmission controller 113 repeatedly switches the pulse production FET 142 on and off at a constant timing by means of a timing pulse signal, and turns on the shunt FET 143 when the pulse production FET 142 is off. In addition, when receiving from the transducer 111 a received echo signal that is based on the ultrasonic echo, the transmission controller 113 sends a signal for turning off both the pulse production FET 142 and the shunt FET 143.
The level shifter 141 converts the timing pulse entered from the transmission controller 113 into a voltage of several tens of volts and sends a pulse corresponding to the pulse production FET 142 and the shunt FET 143.
The pulse production FET 142 is a switching element for producing a pulse and the shunt FET 143 is a switching element for returning the voltage that has risen to ground the pulse.
When instructing the transducer 111 to generate an ultrasonic pulse (i.e., when sending out an ultrasound beam to the subject to be examined 030), the pulse production FET 142 and the shunt FET 143 output a pulse signal by repeating on/off operations at a constant timing upon receiving a command from the transmission controller 113. At this time, the shunt FET 143 is off when the pulse production FET 142 is on, and the shunt FET 143 becomes on when the pulse production FET 142 turns off. As a result of this, voltage that is increased once by the pulse production FET 142 is grounded instantly. The transducer 111 receives the pulse produced here, and then an ultrasound beam is sent to the subject to be examined 030. Herein, the high-pressure prevention circuit 116 is a diode; a high-voltage pulse sent from the pulser 112 is blocked and not sent to the receiving electronic circuit 114.
When receiving a received echo from the subject to be examined 030, the ultrasound beam is reflected from the subject to be examined 030 and received in the transducer 111 as a received echo. The transducer 111 converts the received echo into a signal and sends the same to the receiving electronic circuit 114. This signal passes through the high-pressure prevention circuit 116 because the voltage thereof is weak. At this time, a transmission/reception controller 113 turns off both the pulse production FET 142 and the shunt FET 143 so that the received echo signal will not flow to the group of pulsers 112. Herein, ‘turning off’ refers to generating a state of high impedance.
Next, operations of the bipolar pulser 112 will be explained. As shown in FIG. 3, the pulser 112 comprises a level shifter 141, a positive pole pulse production FET 142a, a negative pole pulse production FET 142b, a shunt FET 143a for grounding the voltage of the positive pole pulse production FET 142a, and a shunt FET 143b for grounding the voltage of the negative pole pulse production FET 142b. 
Also, in the case of the bipolar pulser 112, as is the case with the unipolar pulser 112, a timing signal for transmission is received from the transmission controller 113, and the level shifter 141 turns the positive pole pulse production FET 142a, the negative pole pulse production FET 142b, the shunt FET 143a, and the shunt FET 143b on and off to produce a bipolar pulse. The transducer 111 receives this pulse and sends out an ultrasound beam to the subject to be examined 030.
Conventionally, for an ultrasonic imaging apparatus having a 1-dimension array probe, an electronic circuit for transmitting/receiving ultrasonic waves (transmitting/receiving circuit) is housed in the ultrasonic imaging apparatus body. This made it possible to conduct an operation test of the transmitting/receiving circuit independently from the ultrasound probe by running a test program in the ultrasonic imaging apparatus body when using the ultrasonic imaging apparatus having a 1-dimension array probe. However, for the ultrasonic imaging apparatus having a 2-dimension array probe as described above, a transmitting/receiving circuit is housed in a probe head. As a result, it became difficult to conduct the operation test of the transmitting/receiving circuit independently from the ultrasound probe by means of the ultrasonic imaging apparatus having a 2-dimension array probe as described above.
In addition, for the abovementioned ultrasonic imaging apparatus, 1,000 or more sets of electronic circuits for performing transmission/reception are housed in the probe head. In other words, the apparatus has 1,000 or more sets of structures in which transducers for actually transmitting/receiving ultrasonic waves, a transmitting circuit for applying a high-pressure pulse to each transducer, and a receiving circuit for amplifying a weak ultrasonic echo received by those transducers are directly connected. Therefore, when there is a local abnormality in those electronic circuits for performing transmissions/receptions, the signal goes missing, likely resulting in an artifact or causing unusual heat generation. However, it is difficult to electrically check whether an enormous electronic circuit is operating properly. Thus, an operation check, for example of an ultrasonic imaging apparatus as described, has been acoustically conducted by transmitting a pulse and receiving an echo for channels of all transducers by means of an external target in which a reflecting plate is placed in a water tank. However, the conventional test method always requires a water tank, and a large amount of labor is necessary to conduct the test. Furthermore, in the conventional test method, the angle setting of the 2-dimension array probe against the external target involves errors for each test, and thus the amplitude of the received echo becomes misaligned for each channel. Therefore, it was difficult to achieve high-integrity test results using the conventional test method.